biomass to hydrocarbons via gasification and pyrolysis
TRANSCRIPT
Thermochemical Biofuels:
Challenges and Opportunities June 14, 2012
Brent Shanks
Steffenson Professor Chemical & Biological Engineering Department
2
• Petroleum at $90/bbl – Gasoline, wholesale & untaxed ~$2.70/gal – Diesel, wholesale & untaxed ~$3.00/gal – Grain Ethanol, corn at $3 & $6.50/bu $2.40 & $3.80/gge
Some Context
Biofuels Digest, May 11, 2012
3
• Requires consistent capital cost and evaluation bases
• Comparative economics, not business-case economics
• Considered commercial or “near-commercial” technology where possible
• Material and energy balances by Aspen Plus, generally
• Location U.S. Gulf Coast, 2011 $
• Biomass at $5.4/GJ (limit 1 million t/yr/plant)
• Coal at $2/GJ
• Estimates for Nth of a kind plants (N = 5-7)
• Stand-alone plant: Feedstock in; Finished fuels out
• Comparisons are based on best available data; design basis and data are often not very complete
* Jim Katzer (ExxonMobil retired, Iowa State University)
Technology Comparison*
Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts, NRC, 2009.
4
Material: Grain (corn) Corn Stover Wood (poplar)
Starch, wt % 72.0 n/m n/m
Cellulose, wt % 2.4 36 40
Hemicellulose, wt % 5.5 26 22
Lignin, wt % 0.2 19 24
Ash, wt % 1.4 12 0.6
Bio-Conversion:
Typical Yields: gge/dry tonne 72 48 50
Thermal-Conversion:
Gasification Yield, gge/dry tonne - 67 72
Pyrolysis Yield, gge/dry tonne - 55 60
Feedstock Cost, $/dry tonne: 255 95 80
Feedstock Cost Component:
Bioconversion, $/gge 3.50* $2.00 $1.60
Gasification, $/gge - $1.40 $1.10
Fast Pyrolysis, $/gge - $1.75 $1.30
Red numbers are first-cut indicator of feedstock cost contribution to product cost
* For Corn at $6.50/bu, DDGS netback reduces this to ~$2.60/gge
Biomass Properties & Fuel Cost Component
FB Gasifier
& Cyclone
Chopping &
Lock hopper
oxygen
biomassTar
Cracking
steam
CO2
Gasification
& Quench
Grinding &
Slurry Prep
oxygen
water
coal
Syngas
Scrubber
Acid Gas
Removal
F-T
Refining
F-T
Synthesis
CO2
FlashRefrigeration
Plant
slag
Flash
methanol
CO2
syngas
Water Gas
Shift
Reg
en
era
tor
H2S + CO2
To Claus/SCOT
HC
Re
co
ve
ry
Recycle
Compr.
finished gasoline &
diesel blendstocks
unconverted syngas+ C1 - C4 FT gases
raw FT
product
Refinery H2 Prod
syncrudelight ends
purge gas Power
Island
net export
electricity
gas
coolingexpander
ATRoxygen steam
dry ash
gas
cooling
Filter
flue gas
• Coal: all components are commercially robust
• Biomass gasification is “essentially commercial”
• Options: Methanol synthesis followed by MTG to produce mainly gasoline, DME
Primarily Finished
Gasoline & Diesel
Some Net
Electricity
Thermochemical: Gasification
Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts, NRC, 2009.
6
Thermochemical: Gasification Feedstock Mode Fuel Price, $/gge
– Coal (CTL) Vent CO2 1.75
– Coal CCS 1.90
– Coal/Biomass (40%) (CBTL) Vent CO2 2.75
– Coal/Biomass (40%) CCS 3.00
– Biomass (BTL) vent CO2 3.60
– Biomass CCS 3.85
-1.00
-0.50
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
Fu
el C
om
pon
ent
Cost
, $/g
ge
Co-produce Recovery
CO2 Disposal
O & M
Coal Feed
Biomass Feed
Capital Recovery
Fuel Component Cost
Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts, NRC, 2009.
7
Biomass Gasification Challenges
• Ash management
• “Tars” conversion
• Scalability
• Reactor technology
– CompactGTL, Syntroleum
– Velocys (25 bpd, May, 2012)
Biomass Fast Pyrolysis*
*Bridgwater et al. in Progress in Thermochemical Biomass Conversion, Bridgwater, ed. (2001) 977.
Biochar
O
O
.c
c.
c.
.c
c.
Cellulose
H2, CO, CH4, CO2
Gas
O
O
OH
OH
OH
O
O
OH
OH
OH
O
OH
O
OHO
OH
O
OH
O
O
O
O
Bio-oil
O
OH
OH
O
HOCH2
O
HO
HO
O
CH2OH
O
OH
OH
O
HOCH2
O
HO
HO
O
CH2OH
O
OH
OH
O
HOCH2
O
OH
OH
O
HOCH2
O
HO
HO
O
CH2OH
O
HO
HO
O
CH2OH
O
OH
OH
O
HOCH2
O
OH
OH
O
HOCH2
O
HO
HO
O
CH2OH
O
HO
HO
O
CH2OH
H2O
Corn stover Bio-oil
Biochar Gas
+ + ~500°C
(~22 GJ m-3) (~1.5 GJ m-3) (~21 MJ kg-1) (~6 MJ kg-1)
Fast Pyrolysis
Composition: Fast Pyrolysis Bio-Oil*
Wt%
Water 20-30
Lignin fragments: insoluble pyrolytic lignin 15-30
Aldehydes: formaldehyde, acetaldehyde, hydroxyacetaldehyde, glyoxal 10-20
Carboxylic acids: formic, acetic, propionic, butyric, pentanoic, hexanoic 10-15
Carbohydrates: cellobiosan, levoglucosan, oligosaccharides 5-10
Phenols: phenol, cresol, guaiacols, syringols 2-5
Furfurals 1-4
Alcohols: methanol, ethanol 2-5
Ketones: acetol (1-hydroxy-2-propanone), cyclopentanone 1-5
*Bridgwater et al.; in Progress in Thermochemical Biomass Conversion, Bridgwater, ed. (2001) 977.
Pyrolysis Severity
Primary Processes Secondary Processes Tertiary Processes
Vapor
Phase
Liquid
Phase
Solid
Phase
Low P
High
P
Low P
High
P
Biomass Charcoal Coke Soot
Primary
Liquids
Primary
Vapors
Light HCs,
Aromatics,
& Oxygenates
Condensed Oils
(phenols, aromatics)
CO, H2,
CO2, H2O
PNA’s, CO,
H2, CO2,
H2O, CH4
Olefins, Aromatics
CO, H2, CO2, H2O
CO, CO2,
H2O
Thermal Conversion Reactions
12
• Fast pyrolysis
– Dynamotive, ENSYN
– Avello
• Catalytic pyrolysis
– KIOR
– Anellotech
• Hydropyrolysis
– GTI
Thermochemical: Pyrolysis
ENSYN, 40 tonne/day
KIOR, 50 ton/day
13
Bio-Oil Upgrading Approach
Water
Wash
Bio-Oil Recovery as
Stage Fractions Biomass
Prep/Pretreatment
Selective thermal
depolymerization
(500º C)
Particulate
Removal
Heavy Ends:
Lignin oligomers
and anhydrosugars
Phenolics and Furans
Light Ends:
Aqueous phase of low MW
carbohydrate-derived
compounds
Anhydro-sugars
Lignin
oligomers
Catalytic
deoxygenation
(200-250º C)
Steam
reforming
(200-250º C)
Ring opening/
deoxygenation
(300-350º C)
Hydrogen
Hydrocarbons
Biomass
Hydrocarbons
Bioasphalt
Lignin-derived
chemicals
14
Schematic of Pyrolyzer–GC/MS System
He
Capillary Separation Column
Gas Chromatograph
Mass Spectrometer
(MS)
Feedstock Pyrolyzer
~ 500 μg
500oC
Cellulose Pyrolysis Products
Anhydro sugars Furans/Pyrans Low mol.
wt. species
Fo
rmic
aci
d
Gly
cola
ldeh
yd
e
Ace
tol
Fu
rfu
ral
Hyd
rox
ym
eth
ylf
urf
ura
l
Lev
og
luco
san
5-m
eth
yl
furf
ura
l
3-f
ura
n m
eth
ano
l 2
-fu
ran
met
han
ol
5-m
eth
yl
furf
ura
l
Ace
tic
acid
Lev
og
luco
san
-fu
ran
ose
An
hyd
rox
ylo
pyra
no
se
2-h
yd
rox
y-3
-met
hyl
cycl
op
ente
n-2
-on
e
Lev
og
luco
seno
ne
1,4
;3,6
-dia
nhyd
ro-g
luco
pyra
nose
Patwardhan, P.; et al. J. Anal. Appl. Pyrolysis 2009, 86, 323
16
Effect of Chain Length
Glucose Cellobiose Maltohexaose Cellulose
LMW 57.42 42.16 41.01 21.42
Furans 19.08 17.44 13.85 5.63
Anhydrosugars 13.65 30.69 40.33 67.59
Levoglucosan 7.01 24.36 33.11 58.78
All numbers are wt%
LMW – Low molecular weight compounds
Patwardhan, P.; et al. J. Anal. Appl. Pyrolysis 2009, 86, 323
17
Cellulose
Depolymerized
fragment
Intermediate
Another
depolymerized
fragment
Levoglucosan
Ponder et. al., J Anal. Appl.Pyrolysis,, 1991
Fragment resulting from the
Glycosidic cleavage of dextran
Proposed Mechanism
Detailed mechanism
Department of Chemical and Biological Engineering
Quantum Chemistry Investigations
Levoglucosan
kmid-chain scission
kring closure
kend-chain scission
Ponder et al., J. Anal. Appl. Pyrolysis 1992, 22, 217-229.
O
OH
OHO
OH
O O
OH
OH
OH+
O-
O
OHOOH
OH
O
OHOH
O
OH
O
CH+
OHOH
O
OH
OH O
OH
OH
O
O
CH+OH
OHO
OHMayes and Broadbelt, submitted
Initiation
Depropagation
18
0
50
100
150
200
Gas ImplicitTHF
ImplicitWater
ΔH
in
kc
al/m
ol
at
77
3K
RadicalIonicConcerted
Concerted Mechanism ΔG in kcal/mol
773K, Implicit THF
53.2
-34.8
0.0
‡
+
Detailed mechanism
Department of Chemical and Biological Engineering
Quantum Chemistry Investigations Results
Mayes and Broadbelt, “Unraveling the Reactions that Unravel Cellulose,” submitted. 19
Reaction pathways included in cellulose fast pyrolysis
Detailed mechanism Pyrolysis mechanism
O
OH
OHOHOH
OH
CH
CH
CH
CH
CH
CH2 OH
O
OH
OH
OH
OH
CH O
CH
CH OH
CH2
OH
OH
CH2
OH
CH O
O
OH
OHOH
O
O H
C
C
C
H
H O H
H
O
C
C
H
H H
O C
C
C
H
H O H
H
O
C
C
H
H
O
OH O
O
OH
OHOH
OH
OH
OH OH
OHOH
OH
O
OH
OH
O
O
OHOH
OH
O
OHOH
OH
O
OHOH
OH
CH2
OH
CH O
OH
C
C
C
C
C
CH2OH
O
H
H OH
H
O H
H
OH
C
C
C
C
C
CH2OH
O
H
H
H
O H
CHOO
CH OH
CH OH
CH OH
CH OH
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Char, CO2, CO, H2O
O
OH
OOHOH
OH
O
OH
OHOHO
OH
O
OHOH
O
OH
O
OH
OOHO
OH
O
OHOOH
OH
O
OHOH
O
OH
O
OHOH
O
O
OHO
OHOOH
OH
OO
OHOH
O
O
OHOH
OH
O
OO
OHOH
O
O
OH
OHOHOH
OH
OHO
OHOOH
OH
O
OHOH
OH
O
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Glucose
Department of Chemical and Biological Engineering
Levoglucosan is formed by
concerted, glycosidic bond
cleavage reactions
in the mid and end of
cellulose chains
All other low molecular
weight products are formed
from glucose through various
reactions like dehydration,
ring opening, ring flipping,
retro aldol, retro Diels-Alder
and Grob fragmentation
20
Experimental data corresponds to Patwardhan et al., Biores. Technol. 2010, 101, 4646-4655
0
10
20
30
40
50
60
550 oC500
oC450
oC400
oC
Mass
yie
ld,
wt.
-%
350 oC
0
2
4
6
8
10
12
14
16
550 oC500
oC450
oC400
oC 350
oC
0.0
0.5
1.0
1.5
2.0
2.5
3.0
550 oC500
oC450
oC400
oC 350
oC
Levoglucosan 5-HMF 2-Furfural Formic acid
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
Expt.
Model
550 oC500
oC450
oC400
oC 350
oC
Effect of temperature on cellulose fast pyrolysis products
Model Predictions Model Predictions
Department of Chemical and Biological Engineering
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
0
20
40
60
80
100
Cellulose
Weig
ht
loss
/M
ass
yie
ld,
wt.
-%
Pyrolysis time, s
Levoglucosan
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
0
1
2
3
4
5
6
7
MW 102
Char
GlycolaldehydeHCOOH
H2O
CO2
2-Furfural
5-HMF
Mass
yie
ld,
wt.
-%
Pyrolysis time, s
Glucose
OH
OH OH
Time evolution of products of cellulose fast pyrolysis
T = 500 oC
P = 1 atm
Mn = 135,554 g/mol
PDI = 2.25
21
22
0
1
2
3
4
0 0.1 0.2 0.3 0.4
Wt
%
mmol of salt/g of cellulose
Acetol
0
10
20
0 0.1 0.2 0.3 0.4
Wt
%
mmol of salt/g of cellulose
Formic acid
0
20
40
60
0 0.1 0.2 0.3 0.4
wt
%
mmol of salt/g of cellulose
Levoglucosan
NaCl KCl
MgCl2 CaCl2
0
1
2
3
4
5
0 0.1 0.2 0.3 0.4
Wt
%
mmol of salt/g of cellulose
Furfural
Patwardhan, P.; et al. Bioresource Technol. 2010, 101, 4646
Alkali/Alkaline Earth Effects
23
0
200
400
600
800
1000
1200
1400
1600
1800
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450
mo
l o
f g
luc
ose
/mo
l o
f m
eta
l io
n
mmol of salt/g of cellulose
NaCl
Ca(OH)2
KCl
“Turnover” Number
Effect of Alkali/Alkaline Earth
Patwardhan, P.; et al. Bioresource Technol. 2010, 101, 4646
24
Proposed Mechanism
Ca2+
Ca2+
25
Lignin Pyrolysis
Ace
tic
acid
Low mol. wt. compounds Phenolic compounds
Patwardhan, P.; et al. submitted 2011
26
Micropyrolysis of Lignin
Phen
ol M
ethox
y p
hen
ol
Eth
yl
phen
ol
Hydro
xy s
tyre
ne
Conif
eryl
alco
hol
Sin
apyl
alco
hol
GC-MS Analysis of Vapors from
Micropyrolysis of Lignin
GC-MS Analysis of Condensed Products from
Micropyrolysis of Lignin
Monomers
Oligomers
Patwardhan, P.; et al. submitted 2011
27
Lignin Monomers
coumaryl
alcohol
coniferyl
alcohol
sinapyl
alcohol
28
0
5
10
15
20
25
30
35
0 500 1000 1500 2000 2500
Are
a %
Mol. Wt. (Da)
CCS Mix
GPC of Lignin Monomers
0
5
10
15
20
25
30
35
0 500 1000 1500 2000 2500
Are
a %
Mol. Wt. (Da)
CCS Mix
CCS Mix Py
0
5
10
15
20
25
30
35
0 500 1000 1500 2000 2500
Are
a %
Mol. Wt. (Da)
CCS Mix
CCS Mix Py
CCSA Mix Py
Patwardhan, P.; et al. ChemSusChem 2012
29
“Passivating” Alkali in Biomass
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
Light Oxygenates Anhydrosugars Furans Phenols
wt%
of bio
mass (
wet
basis
)
Comparison of Different Switchgrass Pretreatments
Switchgrass Control
Acetic Acid
Formic Acid
Nitric Acid
Hydrochloric Acid
Phosphoric Acid
Sulfuric Acid
Kuzhiyil et al. (2012) submitted
30
Increases:
Nutrient Availability
Microbial Activity
Soil Organic Matter
Water Retention & Quality
Crop Yields
Decreases:
Fertilizer Needs
Greenhouse Gas Emissions
Nutrient Leaching
Soil Bulk Density
Terra Preta Oxisol
Biochar Application
31
Carbon Residence Time
100 m
Moderate Temperature High Temperature
Biochar “Average” Structure
Brewer, et al. Environ. Prog. Sustainable Energy 2009, 28, 386-396.
33
• Gasification
issue of scale
• Pyrolysis
issue of product quality
Key Challenges
34
Acknowledgements • Robert Brown
• Jim Katzer
• Pushkaraj Patwardhan
• Klaus Schmidt-Rohr
• Catherine Brewer
• Linda Broadbelt
– Vinu Ravikrishnan
– Heather Mayes
• ConocoPhillips
• U.S. Department of Energy
National Advanced Biofuels Consortium